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Re: RFC: stack/heap collision vulnerability and mitigation with GCC
On 21/06/17 09:46, Richard Earnshaw (lists) wrote:
> On 21/06/17 09:44, Andreas Schwab wrote:
>> On Jun 21 2017, "Richard Earnshaw (lists)" <Richard.Earnshaw@arm.com> wrote:
>>
>>> A mere 256 bytes for the caller would permit 32 x 8byte arguments on the
>>> stack which, with at least 8 parameters passed in registers, would allow
>>> for calls with 40 parameters. There can't be many in that space. Any
>>> function making calls with more than that might need additional probes,
>>> but that's going to be exceedingly rare.
>>
>> With passing structures by value you can have arbitrary large
>> parameters.
>>
>> Andreas.
>>
>
>
> No. Those are passed by copies which appear in the locals portion of
* pointers to copies *
R.
> the frame (so are covered by normal allocation priniciples). Only
> structures of less than 16 bytes are passed by direct copy.
>
> R.
>